要确定是否足以零接近，它将为 0.000000 打印6位小数，东西这样的：

To determine whether it's close enough to zero that it will print as 0.000000 to six decimal places, something like:

fabs(d) < 0.0000005

小误差在处理浮点运算可以得到一般比较复杂，虽然。

Dealing with small inaccuracies in floating-point calculations can get quite complicated in general, though.

如果你想有一个更好的想法是什么珍惜你所拥有，尝试用％G 打印，而不是％F 。

If you want a better idea what value you've got, try printing with %g instead of %f.